﻿using System;
using System.Buffers;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace AssetStudio
{
    public class MhyFile
    {
        private string signature;
        private List<BundleFile.StorageBlock> m_BlocksInfo;
        private List<BundleFile.Node> m_DirectoryInfo;

        public BundleFile.Header m_Header;
        public List<StreamFile> fileList;
        public Mhy mhy;

        public MhyFile(FileReader reader, Mhy mhy)
        {
            this.mhy = mhy;
            reader.Endian = EndianType.LittleEndian;

            signature = reader.ReadStringToNull(4);
            Logger.Verbose($"Parsed signature {signature}");
            if (signature != "mhy0")
                throw new Exception("not a mhy file");

            m_Header = new BundleFile.Header
            {
                version = 6,
                unityVersion = "5.x.x",
                unityRevision = "2017.4.30f1",
                compressedBlocksInfoSize = reader.ReadUInt32(),
                flags = (ArchiveFlags)0x43
            };
            Logger.Verbose($"Header: {m_Header}");
            ReadBlocksInfoAndDirectory(reader);
            using var blocksStream = CreateBlocksStream(reader.FullPath);
            ReadBlocks(reader, blocksStream);
            ReadFiles(blocksStream, reader.FullPath);
            m_Header.size = 8 + m_Header.compressedBlocksInfoSize + m_BlocksInfo.Sum(x => x.compressedSize);
            while (reader.PeekChar() == '\0')
            {
                reader.Position++;
            }
        }

        private void ReadBlocksInfoAndDirectory(FileReader reader)
        {
            var blocksInfo = reader.ReadBytes((int)m_Header.compressedBlocksInfoSize);
            DescrambleHeader(blocksInfo);

            Logger.Verbose($"Descrambled blocksInfo signature {Convert.ToHexString(blocksInfo, 0 , 4)}");
            using var blocksInfoStream = new MemoryStream(blocksInfo, 0x20, (int)m_Header.compressedBlocksInfoSize - 0x20);
            using var blocksInfoReader = new EndianBinaryReader(blocksInfoStream);
            m_Header.uncompressedBlocksInfoSize = blocksInfoReader.ReadMhyUInt();
            Logger.Verbose($"uncompressed blocksInfo size: 0x{m_Header.uncompressedBlocksInfoSize:X8}");
            var compressedBlocksInfo = blocksInfoReader.ReadBytes((int)blocksInfoReader.Remaining);

            var uncompressedBlocksInfo = ArrayPool<byte>.Shared.Rent((int)m_Header.uncompressedBlocksInfoSize);
            var uncompressedBlocksInfoSpan = uncompressedBlocksInfo.AsSpan(0, (int)m_Header.uncompressedBlocksInfoSize);

            try
            {
                var numWrite = LZ4.Instance.Decompress(compressedBlocksInfo, uncompressedBlocksInfoSpan);
                if (numWrite != m_Header.uncompressedBlocksInfoSize)
                {
                    throw new IOException($"Lz4 decompression error, write {numWrite} bytes but expected {m_Header.uncompressedBlocksInfoSize} bytes");
                }

                Logger.Verbose($"Writing block and directory to blocks stream...");
                using var blocksInfoUncompressedStream = new MemoryStream(uncompressedBlocksInfo, 0, (int)m_Header.uncompressedBlocksInfoSize);
                using var blocksInfoUncompressedReader = new EndianBinaryReader(blocksInfoUncompressedStream);
                var nodesCount = blocksInfoUncompressedReader.ReadMhyInt();
                m_DirectoryInfo = new List<BundleFile.Node>();
                Logger.Verbose($"Directory count: {nodesCount}");
                for (int i = 0; i < nodesCount; i++)
                {
                    m_DirectoryInfo.Add(new BundleFile.Node
                    {
                        path = blocksInfoUncompressedReader.ReadMhyString(),
                        flags = blocksInfoUncompressedReader.ReadBoolean() ? 4u : 0,
                        offset = blocksInfoUncompressedReader.ReadMhyInt(),
                        size = blocksInfoUncompressedReader.ReadMhyUInt()
                    });

                    Logger.Verbose($"Directory {i} Info: {m_DirectoryInfo[i]}");
                }

                var blocksInfoCount = blocksInfoUncompressedReader.ReadMhyInt();
                m_BlocksInfo = new List<BundleFile.StorageBlock>();
                Logger.Verbose($"Blocks count: {blocksInfoCount}");
                for (int i = 0; i < blocksInfoCount; i++)
                {
                    m_BlocksInfo.Add(new BundleFile.StorageBlock
                    {
                        compressedSize = (uint)blocksInfoUncompressedReader.ReadMhyInt(),
                        uncompressedSize = blocksInfoUncompressedReader.ReadMhyUInt(),
                        flags = (StorageBlockFlags)0x43
                    });

                    Logger.Verbose($"Block {i} Info: {m_BlocksInfo[i]}");
                }
            }
            finally
            {
                ArrayPool<byte>.Shared.Return(uncompressedBlocksInfo, true);
            }    
        }

        private Stream CreateBlocksStream(string path)
        {
            Stream blocksStream;
            var uncompressedSizeSum = (int)m_BlocksInfo.Sum(x => x.uncompressedSize);
            Logger.Verbose($"Total size of decompressed blocks: 0x{uncompressedSizeSum:X8}");
            if (uncompressedSizeSum >= int.MaxValue)
                blocksStream = new FileStream(path + ".temp", FileMode.Create, FileAccess.ReadWrite, FileShare.None, 4096, FileOptions.DeleteOnClose);
            else
                blocksStream = new MemoryStream(uncompressedSizeSum);
            return blocksStream;
        }

        private void ReadBlocks(EndianBinaryReader reader, Stream blocksStream)
        {
            foreach (var blockInfo in m_BlocksInfo)
            {
                var compressedSize = (int)blockInfo.compressedSize;
                var uncompressedSize = (int)blockInfo.uncompressedSize;
                if (compressedSize < 0x10)
                {
                    throw new Exception($"Wrong compressed length: {compressedSize}");
                }

                var compressedBytes = ArrayPool<byte>.Shared.Rent(compressedSize);
                var uncompressedBytes = ArrayPool<byte>.Shared.Rent(uncompressedSize);

                try
                {
                    var compressedBytesSpan = compressedBytes.AsSpan(0, compressedSize);
                    var uncompressedBytesSpan = uncompressedBytes.AsSpan(0, uncompressedSize);

                    reader.Read(compressedBytesSpan);
                    DescrambleEntry(compressedBytesSpan);

                    Logger.Verbose($"Descrambled block signature {Convert.ToHexString(compressedBytes, 0, 4)}");
                    var numWrite = LZ4.Instance.Decompress(compressedBytesSpan[0xC..], uncompressedBytesSpan);
                    if (numWrite != uncompressedSize)
                    {
                        throw new IOException($"Lz4 decompression error, write {numWrite} bytes but expected {uncompressedSize} bytes");
                    }

                    blocksStream.Write(uncompressedBytesSpan);
                }
                finally
                {
                    ArrayPool<byte>.Shared.Return(compressedBytes, true);
                    ArrayPool<byte>.Shared.Return(uncompressedBytes, true);
                }
            }
        }

        private void ReadFiles(Stream blocksStream, string path)
        {
            Logger.Verbose($"Writing files from blocks stream...");

            fileList = new List<StreamFile>();
            for (int i = 0; i < m_DirectoryInfo.Count; i++)
            {
                var node = m_DirectoryInfo[i];
                var file = new StreamFile();
                fileList.Add(file);
                file.path = node.path;
                file.fileName = Path.GetFileName(node.path);
                if (node.size >= int.MaxValue)
                {
                    var extractPath = path + "_unpacked" + Path.DirectorySeparatorChar;
                    Directory.CreateDirectory(extractPath);
                    file.stream = new FileStream(extractPath + file.fileName, FileMode.Create, FileAccess.ReadWrite, FileShare.ReadWrite);
                }
                else
                    file.stream = new MemoryStream((int)node.size);
                blocksStream.Position = node.offset;
                blocksStream.CopyTo(file.stream, node.size);
                file.stream.Position = 0;
            }
        }

        #region Scramble
        private static readonly byte[] GF256Exp = new byte[] { 0x01, 0x03, 0x05, 0x0F, 0x11, 0x33, 0x55, 0xFF, 0x1A, 0x2E, 0x72, 0x96, 0xA1, 0xF8, 0x13, 0x35, 0x5F, 0xE1, 0x38, 0x48, 0xD8, 0x73, 0x95, 0xA4, 0xF7, 0x02, 0x06, 0x0A, 0x1E, 0x22, 0x66, 0xAA, 0xE5, 0x34, 0x5C, 0xE4, 0x37, 0x59, 0xEB, 0x26, 0x6A, 0xBE, 0xD9, 0x70, 0x90, 0xAB, 0xE6, 0x31, 0x53, 0xF5, 0x04, 0x0C, 0x14, 0x3C, 0x44, 0xCC, 0x4F, 0xD1, 0x68, 0xB8, 0xD3, 0x6E, 0xB2, 0xCD, 0x4C, 0xD4, 0x67, 0xA9, 0xE0, 0x3B, 0x4D, 0xD7, 0x62, 0xA6, 0xF1, 0x08, 0x18, 0x28, 0x78, 0x88, 0x83, 0x9E, 0xB9, 0xD0, 0x6B, 0xBD, 0xDC, 0x7F, 0x81, 0x98, 0xB3, 0xCE, 0x49, 0xDB, 0x76, 0x9A, 0xB5, 0xC4, 0x57, 0xF9, 0x10, 0x30, 0x50, 0xF0, 0x0B, 0x1D, 0x27, 0x69, 0xBB, 0xD6, 0x61, 0xA3, 0xFE, 0x19, 0x2B, 0x7D, 0x87, 0x92, 0xAD, 0xEC, 0x2F, 0x71, 0x93, 0xAE, 0xE9, 0x20, 0x60, 0xA0, 0xFB, 0x16, 0x3A, 0x4E, 0xD2, 0x6D, 0xB7, 0xC2, 0x5D, 0xE7, 0x32, 0x56, 0xFA, 0x15, 0x3F, 0x41, 0xC3, 0x5E, 0xE2, 0x3D, 0x47, 0xC9, 0x40, 0xC0, 0x5B, 0xED, 0x2C, 0x74, 0x9C, 0xBF, 0xDA, 0x75, 0x9F, 0xBA, 0xD5, 0x64, 0xAC, 0xEF, 0x2A, 0x7E, 0x82, 0x9D, 0xBC, 0xDF, 0x7A, 0x8E, 0x89, 0x80, 0x9B, 0xB6, 0xC1, 0x58, 0xE8, 0x23, 0x65, 0xAF, 0xEA, 0x25, 0x6F, 0xB1, 0xC8, 0x43, 0xC5, 0x54, 0xFC, 0x1F, 0x21, 0x63, 0xA5, 0xF4, 0x07, 0x09, 0x1B, 0x2D, 0x77, 0x99, 0xB0, 0xCB, 0x46, 0xCA, 0x45, 0xCF, 0x4A, 0xDE, 0x79, 0x8B, 0x86, 0x91, 0xA8, 0xE3, 0x3E, 0x42, 0xC6, 0x51, 0xF3, 0x0E, 0x12, 0x36, 0x5A, 0xEE, 0x29, 0x7B, 0x8D, 0x8C, 0x8F, 0x8A, 0x85, 0x94, 0xA7, 0xF2, 0x0D, 0x17, 0x39, 0x4B, 0xDD, 0x7C, 0x84, 0x97, 0xA2, 0xFD, 0x1C, 0x24, 0x6C, 0xB4, 0xC7, 0x52, 0xF6, 0x01 };
        private static readonly byte[] GF256Log = new byte[] { 0x00, 0x00, 0x19, 0x01, 0x32, 0x02, 0x1A, 0xC6, 0x4B, 0xC7, 0x1B, 0x68, 0x33, 0xEE, 0xDF, 0x03, 0x64, 0x04, 0xE0, 0x0E, 0x34, 0x8D, 0x81, 0xEF, 0x4C, 0x71, 0x08, 0xC8, 0xF8, 0x69, 0x1C, 0xC1, 0x7D, 0xC2, 0x1D, 0xB5, 0xF9, 0xB9, 0x27, 0x6A, 0x4D, 0xE4, 0xA6, 0x72, 0x9A, 0xC9, 0x09, 0x78, 0x65, 0x2F, 0x8A, 0x05, 0x21, 0x0F, 0xE1, 0x24, 0x12, 0xF0, 0x82, 0x45, 0x35, 0x93, 0xDA, 0x8E, 0x96, 0x8F, 0xDB, 0xBD, 0x36, 0xD0, 0xCE, 0x94, 0x13, 0x5C, 0xD2, 0xF1, 0x40, 0x46, 0x83, 0x38, 0x66, 0xDD, 0xFD, 0x30, 0xBF, 0x06, 0x8B, 0x62, 0xB3, 0x25, 0xE2, 0x98, 0x22, 0x88, 0x91, 0x10, 0x7E, 0x6E, 0x48, 0xC3, 0xA3, 0xB6, 0x1E, 0x42, 0x3A, 0x6B, 0x28, 0x54, 0xFA, 0x85, 0x3D, 0xBA, 0x2B, 0x79, 0x0A, 0x15, 0x9B, 0x9F, 0x5E, 0xCA, 0x4E, 0xD4, 0xAC, 0xE5, 0xF3, 0x73, 0xA7, 0x57, 0xAF, 0x58, 0xA8, 0x50, 0xF4, 0xEA, 0xD6, 0x74, 0x4F, 0xAE, 0xE9, 0xD5, 0xE7, 0xE6, 0xAD, 0xE8, 0x2C, 0xD7, 0x75, 0x7A, 0xEB, 0x16, 0x0B, 0xF5, 0x59, 0xCB, 0x5F, 0xB0, 0x9C, 0xA9, 0x51, 0xA0, 0x7F, 0x0C, 0xF6, 0x6F, 0x17, 0xC4, 0x49, 0xEC, 0xD8, 0x43, 0x1F, 0x2D, 0xA4, 0x76, 0x7B, 0xB7, 0xCC, 0xBB, 0x3E, 0x5A, 0xFB, 0x60, 0xB1, 0x86, 0x3B, 0x52, 0xA1, 0x6C, 0xAA, 0x55, 0x29, 0x9D, 0x97, 0xB2, 0x87, 0x90, 0x61, 0xBE, 0xDC, 0xFC, 0xBC, 0x95, 0xCF, 0xCD, 0x37, 0x3F, 0x5B, 0xD1, 0x53, 0x39, 0x84, 0x3C, 0x41, 0xA2, 0x6D, 0x47, 0x14, 0x2A, 0x9E, 0x5D, 0x56, 0xF2, 0xD3, 0xAB, 0x44, 0x11, 0x92, 0xD9, 0x23, 0x20, 0x2E, 0x89, 0xB4, 0x7C, 0xB8, 0x26, 0x77, 0x99, 0xE3, 0xA5, 0x67, 0x4A, 0xED, 0xDE, 0xC5, 0x31, 0xFE, 0x18, 0x0D, 0x63, 0x8C, 0x80, 0xC0, 0xF7, 0x70, 0x07 };
        private static int GF256Mul(int a, int b) => (a == 0 || b == 0) ? 0 : GF256Exp[(GF256Log[a] + GF256Log[b]) % 0xFF];

        private void DescrambleChunk(Span<byte> input)
        {
            byte[] vector = new byte[input.Length];
            for (int i = 0; i < 3; i++)
            {
                for (int j = 0; j < input.Length; j++)
                {
                    int k = mhy.MhyShiftRow[(2 - i) * 0x10 + j];
                    int idx = j % 8;
                    vector[j] = (byte)(mhy.MhyKey[idx] ^ mhy.SBox[(j % 4 * 0x100) | GF256Mul(mhy.MhyMul[idx], input[k % input.Length])]);
                }
                vector.AsSpan(0, input.Length).CopyTo(input);
            }
        }
        private void Descramble(Span<byte> input, int blockSize, int entrySize)
        {
            var roundedEntrySize = (entrySize + 0xF) / 0x10 * 0x10;
            for (int i = 0; i < roundedEntrySize; i += 0x10)
                DescrambleChunk(input.Slice(i + 4, Math.Min(input.Length - 4, 0x10)));

            for (int i = 0; i < 4; i++)
                input[i] ^= input[i + 4];

            var finished = false;
            var currentEntry = roundedEntrySize + 4;
            while (currentEntry < blockSize && !finished)
            {
                for (int i = 0; i < entrySize; i++)
                {
                    input[i + currentEntry] ^= input[i + 4];
                    if (i + currentEntry >= blockSize - 1)
                    {
                        finished = true;
                        break;
                    }
                }
                currentEntry += entrySize;
            }
        }
        public void DescrambleHeader(Span<byte> input) => Descramble(input, 0x39, 0x1C);
        public void DescrambleEntry(Span<byte> input) => Descramble(input, Math.Min(input.Length, 0x21), 8);
        #endregion
    }
}